It depends. If the person is being called to active duty, use the date they receive their orders.
If they are enlisting, use the date they report for active duty.
I try to think of this as, if the government calls them, they get immediate protection because they weren't given time to prepare. (This would also apply if we still had the draft.) However, if they enlist on their own, they have had time to prepare financially and should be ready to handle their affairs as they have been up until they are on the government's payroll.
_________________________
AndyZ CRCM
My opinions are not necessarily my employers.
R+R-R=R+R
Rules and Regs minus Relationships equals Resentment and Rebellion. John Maxwell